Lipid autoxidation, which results in the formation of hydroperoxides and secondary products, has been implicated in many degenerative diseases, such as atherosclerosis. In order to more fully understand the role of lipid autoxidation in the progression of such diseases, as well as treatment, knowledge of the fundamental chemistry that is occurring is necessary. This research project. is designed to investigate the formation and reactivity of bis-allylic lipid hydroperoxides, which have only recently been identified as products of lipid autoxidation. The tools and theories of organic chemistry, such as synthesis, isotopic labelling experiments, and a new HPLC/Ag-CIS-MS (Ag coordination ionspray mass spectrometry) method will be utilized to investigate the reactivity of the hydroperoxide. This powerful and mild method allows potentially labile, neutral compounds to be analyzed and identified without significant manipulation of the sample. The reactivity of the bis-allylic hydroperoxide in the presence of various anti-oxidants, mechanism and kinetics of formation and rearrangement, and potential biological relevance are the focus of this research.